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SubjectRe: BUG: GCC-4.4.x changes the function frame on some functions
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On Thu, 2009-11-19 at 11:50 -0800, H. Peter Anvin wrote:

> > Perhaps we could create another profiler? Instead of calling mcount,
> > call a new function: __fentry__ or something. Have it activated with
> > another switch. This could make the performance of the function tracer
> > even better without all these exceptions.
> >
> > <function>:
> > call __fentry__
> > [...]
> >
>
> Calling the profiler immediately at the entry point is clearly the more
> sane option. It means the ABI is well-defined, stable, and independent
> of what the actual function contents are. It means that ABI isn't the
> normal C ABI (the __fentry__ function would have to preserve all
> registers), but that's fine...

mcount already has that requirement (saving all/most regs). Anyway, you
are right, we don't care. The tracer should carry the blunt of the load,
not the individual callers.

-- Steve




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